CN108191008B - Preparation method and application of Pd/TiN electro-catalytic electrode - Google Patents
Preparation method and application of Pd/TiN electro-catalytic electrode Download PDFInfo
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Abstract
The application provides a preparation method and application of a Pd/TiN electro-catalytic electrode, and the preparation method and application form a nano titanium nitride and nano Pd particle interface by loading Pd nano particles on nano titanium nitride particles, and the titanium nitride transfers electrons to Pd through the interface, so that Pd forms an electron-rich state, thereby optimizing the adsorption of the nano titanium nitride and the desorption of dechlorination products, accelerating the reaction rate, improving the intrinsic electro-catalytic activity of palladium and further improving the dechlorination efficiency. In the application, a sodium hydroxide solution is added to regulate and control the pH of the system, a precursor sodium chloropalladate of palladium is converted into an intermediate palladium hydroxide, and palladium atoms are uniformly loaded on the surface of titanium nitride in a palladium hydroxide precipitation mode, so that the dispersity of palladium on a carrier can be improved, and reaction active sites can be increased. In addition, the Pd/TiN electrode prepared by the method has high selectivity, few byproducts and good electrode conductivity, and does not need to be additionally added with carbon powder to enhance the conductivity.
Description
Technical Field
The application relates to the technical field of electrochemical water treatment, in particular to a preparation method and application of a Pd/TiN electro-catalysis electrode.
Background
The chlorine-containing organic matters comprise chlorinated hydrocarbons, chlorinated aromatic hydrocarbons, organochlorine pesticides (such as polychlorinated biphenyl), organochlorine pesticides and the like, and are important modern chemical production raw materials and intermediates. However, most chlorinated organic compounds have certain toxicity, especially carcinogenicity, teratogenicity and mutagenicity of chlorinated aromatic organic compounds, so that the chlorinated organic compounds become priority control pollutants published by European Union and United states environmental protection agency. In addition, chlorine-containing organic matters are difficult to naturally degrade, have durability in the environment, and are widely present in water, soil and atmosphere, thus seriously affecting the normal production and life of people.
The treatment method for chlorine-containing wastewater mainly comprises a physical method, a chemical method and a biological method. The physical method mainly comprises sealing, burying, flocculating settling, extracting, adsorbing, microwave treating and the like, but the physical method has smaller treating capacity and no degradation process, can not completely decompose or harmlessly treat pollutants, has the risk of secondary pollution, and also needs subsequent treatment. Conventional chemical methods mainly include incineration, oxidation, metal reduction, and the like, and also have many problems of secondary pollution and unstable treatment efficiency. The biological method is environment-friendly and is the most widely applied technology in the current sewage treatment, but the biotoxicity of the chlorine-containing organic matters causes the low treatment efficiency and the long degradation time.
At present, attempts are made to reduce the toxicity of chlorine-containing wastewater by removing chlorine atoms through pretreatment, and a common technology is electrocatalytic dechlorination technology, namely palladium (Pd) is used as a catalyst, but the Pd catalyst is expensive. In order to reduce the cost, the intrinsic electrocatalytic activity of Pd is increased, and the dosage of Pd is reduced. Therefore, the research on the novel Pd supported catalyst improves the intrinsic electrocatalytic activity of Pd, obtains the novel electrocatalytic material which has high dechlorination efficiency, strong stability, good repeatability and good conductivity, is environment-friendly, and has great practical significance and economic significance.
Disclosure of Invention
The application provides a preparation method and application of a Pd/TiN electro-catalytic electrode, which are used for improving the intrinsic electro-catalytic activity of Pd.
In order to solve the technical problem, the embodiment of the application discloses the following technical scheme:
the application provides a preparation method of a Pd/TiN electrocatalytic electrode, which comprises the following steps:
s01: weighing a certain amount of TiN, soaking the TiN in concentrated hydrochloric acid, performing ultrasonic treatment for 10-30 min, then stirring, finally filtering and washing the TiN for 3-5 times by using deionized water, and putting the TiN into a constant-temperature oven for drying to obtain dry TiN;
s02: ultrasonically dispersing the dry TiN in deionized water to obtain TiN dispersion liquid, slowly dropwise adding a sodium chloropalladate solution into the TiN dispersion liquid to obtain a mixed liquid, and ultrasonically dispersing the mixed liquid for 30min, and dropwise adding a sodium hydroxide solution to obtain a first suspension liquid;
s03: stirring the first suspension for 10-30 min, and gradually stirringDropwise adding NaBH4Stirring the solution, and standing the suspension after the reaction is finished to obtain a second suspension;
s04: after the second suspension is layered, removing supernatant, washing and precipitating for 3-5 times by using deionized water, and drying in a constant-temperature oven to obtain the Pd/TiN composite material;
s05: preparing carbon paper coated with copper glue and silica gel for later use;
s06: weighing a certain amount of Pd/TiN composite material, dispersing in ethanol to obtain Pd/TiN-ethanol dispersion liquid, adding an adhesive to obtain a third suspension liquid, carrying out ultrasonic treatment until the third suspension liquid is uniformly mixed and dispersed, taking the third suspension liquid, dripping the third suspension liquid to a blank area of the carbon paper, and obtaining the Pd/TiN electro-catalytic electrode after the third suspension liquid is completely coated.
Preferably, the manufacturing of the carbon paper coated with the copper paste and the silica gel comprises: cutting carbon paper with a certain size, folding copper glue with a certain length, respectively sticking the carbon paper to the front side and the back side of the carbon paper, and smearing silica gel in a copper glue sticking area of the carbon paper;
preferably, in S01, the concentration ratio of TiN to concentrated hydrochloric acid is 5-15: 1; in the S01, the stirring temperature is set to be 50-80 ℃, and the stirring time is 0.5-2 h; the temperature of the constant-temperature oven is set to be 60-80 ℃.
Preferably, in the S02, the TiN dispersion liquid has a concentration of 0.5-2 g/L, the mixed liquid has a concentration of about 0.01-0.5 g/L, and the first suspension has a pH of 9-12.
Preferably, in the step S03, the stirring speed is set to be 300-800 rpm, and the stirring time is 2-3 hours; the NaBH4The concentration of the solution is 10-30 g/L.
Preferably, in S04, the temperature of the constant temperature oven is set to 60 to 80 ℃.
Preferably, in the S06, the concentration of the Pd/TiN-ethanol dispersion liquid is 5-8 g/L, and the concentration of the adhesive is 0.005-0.02 g/L.
The application also provides application of the Pd/TiN electrocatalytic electrode prepared by any one of the claims above in removing chlorine atoms in chlorine-containing wastewater.
The beneficial effect of this application does:
the application provides a preparation method and application of a Pd/TiN electro-catalytic electrode, and the preparation method and application form a nano titanium nitride and nano Pd particle interface by loading Pd nano particles on nano titanium nitride particles, and the titanium nitride transfers electrons to Pd through the interface, so that Pd forms an electron-rich state, thereby optimizing the adsorption of the nano titanium nitride and the desorption of dechlorination products, accelerating the reaction rate, improving the intrinsic electro-catalytic activity of palladium and further improving the dechlorination efficiency. In the application, a sodium chloropalladate precursor of palladium is converted into an intermediate palladium hydroxide by adding a sodium hydroxide solution to regulate and control the pH of a system, palladium atoms are uniformly loaded on the surface of titanium nitride in a palladium hydroxide precipitation mode, and a reducing agent is not directly used for reducing the sodium chloropalladate solution, so that the dispersity of palladium on a carrier can be improved, and reaction active sites are increased. In addition, the Pd/TiN electrode prepared by the method has high selectivity, few byproducts and good electrode conductivity, and does not need to be additionally added with carbon powder to enhance the conductivity.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.
FIG. 1 is a schematic flow chart of a method for preparing a Pd/TiN electrocatalytic electrode according to an embodiment of the invention;
FIG. 2 is a TEM, HRTEM and XRD test chart of a Pd/TiN electrocatalytic electrode provided by an embodiment of the invention;
wherein a is an electrode direct view photograph of the Pd/TiN electrocatalytic electrode provided by the embodiment of the invention; b is a TEM test image (scanning electron micrograph); c is HRTEM test pattern (high resolution scanning electron microscope); d is XRD test pattern (X-ray diffraction analysis).
FIG. 3 is a schematic structural diagram of a dechlorination apparatus according to an embodiment of the present invention;
description of reference numerals: 1-working electrode, 2-reference electrode, 3-counter electrode, 4-cation exchange membrane, 5-stirrer, 6-electrochemical workstation, 7-anode chamber, 8-cathode chamber.
FIG. 4 is a schematic diagram of the Pd/TiN electrocatalytic electrode provided herein as a function of 2, 4-dichlorophenol dechlorination efficiency with reaction time;
FIG. 5 is a schematic diagram of the distribution of the dechlorinated 2, 4-dichlorophenol by the Pd/TiN electro-catalytic electrode.
Detailed Description
In order to make those skilled in the art better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Referring to fig. 1, a flow chart of a method for manufacturing a Pd/TiN electrocatalytic electrode according to embodiments of the present application is shown, and the following embodiments are based on the flow steps shown in fig. 1. As can be seen from fig. 1, the method comprises the following steps:
s01: weighing a certain amount of TiN, soaking the TiN in concentrated hydrochloric acid, performing ultrasonic treatment for 10-30 min, then stirring, finally filtering and washing the TiN for 3-5 times by using deionized water, and putting the TiN into a constant-temperature oven for drying to obtain dry TiN;
s02: ultrasonically dispersing the dry TiN in deionized water to obtain TiN dispersion liquid, slowly dropwise adding a sodium chloropalladate solution into the TiN dispersion liquid to obtain a mixed liquid, and ultrasonically dispersing the mixed liquid for 30min, and dropwise adding a sodium hydroxide solution to obtain a first suspension liquid;
s03: stirring the first suspension for 10-30 min, and then dropwise adding NaBH4Stirring the solution, and standing the suspension after the reaction is finished to obtain a second suspension;
s04: after the second suspension is layered, removing supernatant, washing and precipitating for 3-5 times by using deionized water, and drying in a constant-temperature oven to obtain the Pd/TiN composite material;
s05: preparing carbon paper coated with copper glue and silica gel for later use;
s06: weighing a certain amount of Pd/TiN composite material, dispersing in ethanol to obtain Pd/TiN-ethanol dispersion liquid, adding an adhesive to obtain a third suspension liquid, carrying out ultrasonic treatment until the third suspension liquid is uniformly mixed and dispersed, taking the third suspension liquid, dripping the third suspension liquid to a blank area of the carbon paper, and obtaining the Pd/TiN electro-catalytic electrode after the third suspension liquid is completely coated.
Example 1:
the embodiment provides a preparation method of a Pd/TiN electrocatalytic electrode, which comprises the following steps:
s101: weighing 200mg of TiN, adding 30mL of concentrated hydrochloric acid, putting into an ultrasonic cleaning instrument for ultrasonic treatment for 10min, taking out, putting into a constant-temperature magnetic stirrer, stirring for 2h at the water temperature of 60 ℃, washing and filtering for 3 times by using deionized water, putting into a baking oven at the temperature of 60 ℃, and drying;
s102: weighing 20mg of dried TiN, ultrasonically dispersing in 30mL of deionized water, slowly dropwise adding 1mL of 3g/L sodium chloropalladate solution, ultrasonically reacting for 20min, and adjusting the pH value of the suspension to 10 by using 30g/L sodium hydroxide solution after stopping ultrasonic treatment to obtain a first suspension;
s103: placing the first suspension on a magnetic stirrer at the rotation speed of 500rpm, stirring for 10min, and then dropwise adding the prepared 20g/L NaBH4Stirring 10mL of aqueous solution for reacting for 2h, and standing the suspension to obtain a second suspension;
s104: after the second suspension is kept stand and layered, removing supernatant, washing the second suspension for 3 times by using deionized water, and drying the second suspension in a drying oven at the temperature of 60 ℃ to obtain the Pd/TiN composite material;
s105: cutting 3 x 3cm2Cutting out copper glue with the length of 2cm, folding the copper glue in half, respectively sticking the copper glue to the front side and the back side of the carbon paper, reserving the carbon paper with the length of 0.5cm, and smearing the carbon paper with the thickness of 1mm in the area stuck with the copper glue by using the silica gel;
s106: dispersing 24mg of Pd/TiN composite material in 4mL of ethanol to obtain Pd/TiN-ethanol dispersion liquid, adding 40 mu L of Nafion as an adhesive to obtain third suspension liquid, carrying out ultrasonic treatment until the third suspension liquid is uniformly mixed and dispersed, taking the third suspension liquid by using a dropper, and dropping the third suspension liquid onto a blank area (2 x 3 cm) of carbon paper2) Each dripping can be carried out after the liquid coated last time is completely volatilized, and the Pd/TiN electro-catalytic electrode can be obtained after the dripping is finished.
Example 2:
the embodiment provides a preparation method of a Pd/TiN electrocatalytic electrode, which comprises the following steps:
s201: weighing 250mg of TiN, adding 30mL of concentrated hydrochloric acid, putting into an ultrasonic cleaning instrument for ultrasonic treatment for 20min, taking out, putting into a constant-temperature magnetic stirrer, stirring for 1.5h at 70 ℃ of water, washing and filtering for 4 times by using deionized water, putting into a 70 ℃ oven, and drying;
s202: weighing 30mg of dried TiN, ultrasonically dispersing in 40mL of deionized water, slowly dropwise adding 2mL of 3g/L sodium chloropalladate solution, ultrasonically reacting for 20min, and adjusting the pH value of the suspension to 11 by using 30g/L sodium hydroxide solution after stopping ultrasonic treatment to obtain a first suspension;
s203: placing the first suspension on a magnetic stirrer at the rotation speed of 600rpm, stirring for 20min, and then dropwise adding the prepared 20g/L NaBH4Stirring 15mL of aqueous solution for reacting for 2.5h, and standing the suspension to obtain a second suspension;
s204: after the second suspension is kept stand and layered, removing supernatant, washing the second suspension for 4 times by using deionized water, and drying the second suspension in a 70 ℃ oven to obtain the Pd/TiN composite material;
s205: cutting 3 x 3cm2Cutting out copper glue with the length of 2cm, folding the copper glue in half, respectively sticking the copper glue to the front side and the back side of the carbon paper, reserving the copper glue with the length of 0.5cm, and smearing the copper glue on the carbon paper area stuck with the copper glue by using the silica glueThe thickness is 1 mm;
s206: dispersing 24mg of Pd/TiN composite material in 4mL of ethanol to obtain Pd/TiN-ethanol dispersion liquid, adding 40 mu L of Nafion as an adhesive to obtain third suspension liquid, carrying out ultrasonic treatment until the third suspension liquid is uniformly mixed and dispersed, taking the third suspension liquid by using a dropper, and dropping the third suspension liquid onto a blank area (2 x 3 cm) of carbon paper2) Each dripping can be carried out after the liquid coated last time is completely volatilized, and the Pd/TiN electro-catalytic electrode can be obtained after the dripping is finished.
Example 3:
the embodiment provides a preparation method of a Pd/TiN electrocatalytic electrode, which comprises the following steps:
s301: weighing 300mg of TiN, adding 40mL of concentrated hydrochloric acid, putting into an ultrasonic cleaning instrument for ultrasonic treatment for 30min, taking out, putting into a constant-temperature magnetic stirrer, stirring for 0.5h at the water temperature of 80 ℃, washing with deionized water, filtering for 5 times, putting into an oven at the temperature of 80 ℃, and drying;
s302: weighing 20mg of dried TiN, ultrasonically dispersing in 30mL of deionized water, slowly dropwise adding 1mL of 3g/L sodium chloropalladate solution, ultrasonically reacting for 20min, and adjusting the pH value of the suspension to 12 by using 30g/L sodium hydroxide solution after stopping ultrasonic treatment to obtain a first suspension;
s303: placing the first suspension on a magnetic stirrer at the rotating speed of 800rpm, stirring for 30min, and then dropwise adding the prepared 20g/L NaBH4Stirring 20mL of aqueous solution for reacting for 3h, and standing the suspension to obtain a second suspension;
s304: after the second suspension is kept stand and layered, removing supernatant, washing the second suspension for 5 times by using deionized water, and drying the second suspension in a drying oven at the temperature of 60 ℃ to obtain the Pd/TiN composite material;
s305: cutting 3 x 3cm2Cutting out copper glue with the length of 2cm, folding the copper glue in half, respectively sticking the copper glue to the front side and the back side of the carbon paper, reserving the carbon paper with the length of 0.5cm, and smearing the carbon paper with the thickness of 1mm in the area stuck with the copper glue by using the silica gel;
s306: dispersing 24mg of Pd/TiN composite material in 4mL of ethanol to obtain Pd/TiN-ethanol dispersion liquid, adding 40 mu L of Nafion as an adhesive to obtain third suspension liquid, and carrying out ultrasonic treatment until the third suspension liquid is obtainedThe suspension is mixed and dispersed evenly, and a third suspension is taken by a dropper and dropped on a blank area (2 x 3 cm)2) Each dripping can be carried out after the liquid coated last time is completely volatilized, and the Pd/TiN electro-catalytic electrode can be obtained after the dripping is finished.
To evaluate the properties of the Pd/TiN electrocatalytic electrodes provided herein, the present application also provides the following tests:
firstly, a Pd/TiN electrocatalytic electrode is subjected to TEM (scanning electron microscope image), HRTEM (high resolution scanning electron microscope) and XRD (X-ray diffraction analysis) tests in the embodiment of the invention, specifically referring to FIG. 2, FIG. 2 is a TEM, HRTEM and XRD test picture of the Pd/TiN electrocatalytic electrode provided in the embodiment of the invention, and as can be seen from the picture, the Pd/TiN electrocatalytic electrode provided in the embodiment of the invention has black appearance and can be uniformly distributed on carbon paper; the TEM figure shows that Pd nanoparticles can be uniformly supported on TiN and the particle size is about 5 nm; in HRTEM image, the lattice spacing of (111) crystal plane of Pd nano-particle is 0.23nm, the lattice spacing of (220) crystal plane of titanium nitride is 0.21nm, and the existence of Pd nano-particle and titanium nitride is confirmed; all five obvious diffraction peaks in XRD are from titanium nitride, which shows that the Pd nano-particles are used in a small amount in the electrode and have small particle size. The above results confirm that the Pd/TiN electrocatalytic electrode can be successfully obtained by the preparation method provided by the invention.
Secondly, in order to evaluate the catalytic activity of the Pd/TiN electrocatalytic electrode provided by the embodiment of the invention in dechlorination reaction, the dechlorination effect of the Pd/TiN electrocatalytic electrode on 2, 4-dichlorophenol is examined, and the specific method is as follows:
(1) building a dechlorination reaction device: with specific reference to fig. 3, fig. 3 is a schematic structural diagram of a dechlorination apparatus according to an embodiment of the present invention; the electrolytic cell is an H-shaped electrolytic cell, the anode chamber and the cathode chamber are separated by a cation exchange membrane, and the volumes of the anode chamber and the cathode chamber are both 200 mL; respectively adding 100ml of 0.05mol/L sodium sulfate electrolyte into the anode chamber and the cathode chamber; introducing nitrogen gas into the electrolytes of the anode chamber and the cathode chamber for 5min, adding 2, 4-dichlorophenol stock solution into the cathode electrolytic chamber by using a pipette to enable the initial concentration to be 50mg/L, and adding a B-type magnetic stirrer for stirring; according to the principle of a three-electrode system, a circuit of the electrocatalytic dechlorination device is built. Wherein the counter electrode is a platinum sheet electrode (size 30 mm. times.30 mm), the reference electrode is Ag/AgCl (3.0M KCl), and the working electrode is the Pd/TiN electrocatalytic electrode prepared in the example 1 of the present invention.
(2) Operation of the dechlorination reaction device:
the whole dechlorination experimental device is placed in a constant-temperature water bath magnetic stirrer at the temperature of 25 ℃, and is stirred at a constant speed of 400 rpm;
setting parameters of an electrochemical workstation, selecting an ampere-counting method, setting the voltage to be-0.8V, and starting the electro-catalytic hydrodechlorination reaction.
(3) Determining the dechlorination activity of the Pd/TiN electro-catalytic electrode, comprising the following steps:
when the reaction is carried out for 0, 5, 10, 20, 30, 60, 120, 180, 240, 300 and 360min, a glass syringe is used for sampling the reaction solution in the cathode chamber and placing the reaction solution into a chromatographic sampling bottle;
respectively measuring the concentrations of 2, 4-dichlorophenol, 4-chlorophenol, 2-chlorophenol and phenol in the sample injection bottle by using a high performance liquid chromatograph (SHIMADZU 2010-AT);
and substituting the peak areas of all substances measured in the liquid chromatogram into corresponding standard curves, calculating the concentrations of the substances, and drawing a curve of dechlorination efficiency of the Pd/TiN electro-catalytic electrode on 2, 4-dichlorophenol, which is provided by the embodiment of the invention, along with time and a product distribution diagram according to the results.
The formula for calculating the dechlorination efficiency is as follows: eta ═ C0-C)/C0×100％
Wherein eta is dechlorination efficiency (%), C0Is the initial concentration (mg/L) of 2, 4-dichlorophenol, and C is the concentration (mg/L) of 2, 4-dichlorophenol measured at the sampling time.
With specific reference to fig. 4, fig. 4 is a schematic diagram of the Pd/TiN electrocatalytic electrode provided herein as a function of 2, 4-dichlorophenol dechlorination efficiency with reaction time; the figure shows that the removal rate of 2, 4-dichlorophenol is continuously increased, and after 6 hours of reaction, the removal rate reaches 97.27%, which proves that the Pd/TiN electrocatalytic electrode has strong dechlorination capability; FIG. 5 is a schematic diagram of the distribution of dechlorinated 2, 4-dichlorophenol by a Pd/TiN electro-catalytic electrode according to the present application; it can be seen from the figure that the main dechlorination product obtained by the method provided by the invention is phenol, a small amount of o-chlorophenol is contained, and p-chlorophenol is not detected, which shows that the Pd/TiN electrocatalytic electrode has strong selectivity on phenol, weaker selectivity on o-chlorophenol and p-chlorophenol, and the dechlorination reaction is completely carried out.
Thirdly, the application inspects the influence of different voltages on the dechlorination reaction of the 2, 4-dichlorophenol, and concretely comprises the following steps:
building a dechlorination device;
setting electrocatalysis conditions, changing the voltage setting conditions, respectively setting the voltage values to-0.65V, -0.70V, -0.75V, -0.85V, -0.90V and-0.95V, and carrying out dechlorination reaction under the respective conditions;
obtaining the removal rate of the dechlorination reaction of the Pd/TiN electro-catalysis electrode under different voltages.
The results of the electrocatalytic dechlorination reaction at different voltages are shown in table 1; with the increase of voltage, the amount of active hydrogen generated by electrode reaction is increased continuously, more active hydrogen is available for dechlorination reaction, and dechlorination efficiency is improved. When the voltage reaches-0.8V, the dechlorination efficiency is highest (97.27%), but with the further increase of the voltage, although the yield of active hydrogen is increased, the production amount of hydrogen is also increased rapidly, and the hydrogen not only consumes a large amount of active hydrogen, but also influences the mass transfer diffusion of the 2, 4-dichlorophenol in the solution, thereby inhibiting the dechlorination reaction. Therefore, after the voltage exceeds-0.8V, the dechlorination efficiency is reduced along with the increase of the voltage, so that the best dechlorination effect can be obtained when the-0.8V is the most suitable voltage for the Pd/TiN electric catalytic electrode in the dechlorination reaction.
TABLE 1 dechlorination efficiency of Pd/TiN electrocatalytic electrode dechlorination reaction at different voltages
Fourthly, the application researches Pd/TiN electro-catalytic electrodes with different Pd loading amounts, inspects the influence of the Pd loading amount on the dechlorination effect of the 2, 4-dichlorophenol, and comprises the following use steps:
(1) preparing the Pd/TiN composite material according to the method provided by the application, only changing the addition amount of the sodium chloropalladate solution in the step (1), setting the addition amount to be 2mL, 0.5mL and 0.1mL respectively, and additionally preparing the Pd/TiN composite material with three different Pd loading amounts;
(2) determining the loading amount of the Pd nanoparticles, which comprises the following steps:
a) a certain amount of the three Pd/TiN composite materials and the Pd/TiN composite material obtained in the example 1 are weighed, 5mL of aqua regia is added respectively, and the Pd/TiN composite material is dissolved. After completion of the dissolution, 10mL of 3% dilute nitric acid was added, and filtration was performed after dilution. Taking 1mL of filtered liquid, and diluting with a dilute nitric acid solution with the concentration of 3%;
b) measuring the concentration of Pd ions in the diluted solution by utilizing atomic emission spectroscopy (ICP), and calculating the load amount of Pd in each Pd/TiN composite material according to the following formula:
pd loading (wt%) (C × N × V × 10)-6)/m1×100％
Wherein C is the Pd ion concentration (ppm) by ICP, N is the dilution factor, V is the volume (mL), m1The mass (g) is measured for the Pd/TiN composite material.
(3) Pd/TiN composites with different Pd loading were used to make Pd/TiN electrocatalytic electrodes according to the method of use of example 1;
(4) the dechlorination efficiency of the Pd/TiN electrocatalytic electrode pair with different Pd loadings on 2, 4-dichlorophenol was determined at-0.8V according to the application method of example 2.
The dechlorination efficiencies of the Pd/TiN electrocatalytic electrodes with different Pd loadings are shown in Table 2. When the amount of Pd supported is small, the amount of active sites provided is small, and the dechlorination effect is poor. When the Pd loading is too much, the particles are easy to agglomerate and have poor dispersibility, the amount of available active sites can be reduced, and the dechlorination efficiency is not high. From the results, the dechlorination effect was best when the Pd loading was 6.97 wt%, indicating that the Pd loading on the Pd/TiN electrode was most suitable.
TABLE 2 dechlorination efficiency of Pd/TiN electrodes with different Pd nanoparticle loadings
Fifthly, the application also provides an evaluation method for the repeated use effect of the Pd/TiN electrocatalytic electrode in the 2, 4-dichlorophenol dechlorination reaction under the same voltage. The method comprises the following specific steps:
and (3) carrying out dechlorination for five times for 6 hours to obtain the dechlorination efficiency of the Pd/TiN electro-catalytic electrode to the 2, 4-dichlorophenol under each circulation.
The results of the cycling experiment are shown in table 3, and the results prove that the Pd/TiN electrocatalytic electrode has stable effect, the removal rate of 2, 4-dichlorophenol can be kept around 90% after being repeatedly used for five times, and the removal rate is reduced by only 8.07% compared with the initial removal rate. The Pd/TiN electrocatalytic electrode prepared by the method provided by the invention has better reusability and is beneficial to reducing the use cost of the electrode.
TABLE 3-0.8V results of 5 repetitions of electrocatalytic dechlorination
The embodiment proves that the Pd/TiN electrocatalytic electrode provided by the invention has reliable preparation technology, has good dechlorination effect on chlorine-containing organic matters in water, has high selectivity on the product phenol, does not generate secondary pollution, has high stability and can be repeatedly used. The Pd/TiN electro-catalytic electrode has wide application prospect in restoring water environment polluted by chlorine-containing organic matters through electro-catalytic reduction and dechlorination.
Since the above embodiments are all described by referring to and combining with other embodiments, the same portions are provided between different embodiments, and the same and similar portions between the various embodiments in this specification may be referred to each other. And will not be described in detail herein.
Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the present invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the application being indicated by the following claims.
The above-described embodiments of the present application do not limit the scope of the present application.
Claims (8)
1. A preparation method of a Pd/TiN electrocatalytic electrode is characterized by comprising the following steps:
s01: weighing a certain amount of TiN, soaking the TiN in concentrated hydrochloric acid, performing ultrasonic treatment for 10-30 min, then stirring, finally filtering and washing the TiN for 3-5 times by using deionized water, and putting the TiN into a constant-temperature oven for drying to obtain dry TiN;
s02: ultrasonically dispersing the dry TiN in deionized water to obtain TiN dispersion liquid, slowly dropwise adding a sodium chloropalladate solution into the TiN dispersion liquid to obtain a mixed liquid, ultrasonically dispersing the mixed liquid for 30min, and dropwise adding a sodium hydroxide solution to obtain a first suspension liquid, wherein the pH value of the first suspension liquid is 9-12;
s03: stirring the first suspension for 10-30 min, and then dropwise adding NaBH4Stirring the solution, and standing the suspension after the reaction is finished to obtain a second suspension;
s04: after the second suspension is layered, removing supernatant, washing and precipitating for 3-5 times by using deionized water, and drying in a constant-temperature oven to obtain the Pd/TiN composite material;
s05: preparing carbon paper coated with copper glue and silica gel for later use;
s06: weighing a certain amount of Pd/TiN composite material, dispersing in ethanol to obtain Pd/TiN-ethanol dispersion liquid, adding an adhesive to obtain a third suspension liquid, carrying out ultrasonic treatment until the third suspension liquid is uniformly mixed and dispersed, taking the third suspension liquid, dripping the third suspension liquid to a blank area of the carbon paper, and obtaining the Pd/TiN electro-catalytic electrode after the third suspension liquid is completely coated.
2. The method of claim 1, wherein the making the carbon paper coated with the copper paste and the silica gel comprises: cutting carbon paper with a certain size, folding the carbon paper in half for a certain length, respectively sticking the carbon paper to the front side and the back side of the carbon paper, and smearing silica gel on the carbon paper in a copper adhesive sticking area.
3. The method according to claim 1, wherein in S01, the concentration ratio of TiN to concentrated hydrochloric acid is 5-15: 1;
in the S01, the stirring temperature is set to be 50-80 ℃, and the stirring time is 0.5-2 h;
the temperature of the constant-temperature oven is set to be 60-80 ℃.
4. The method according to claim 1, wherein in S02, the TiN dispersion liquid has a concentration of 0.5-2 g/L, and the mixed liquid has a concentration of 0.01-0.5 g/L.
5. The method according to claim 1, wherein in S03, the stirring speed is set to 300-800 rpm, the stirring time is 2-3 h, and the NaBH is added4The concentration of the solution is 10-30 g/L.
6. The preparation method according to claim 1, wherein in the S04, the temperature of the constant-temperature oven is set to be 60-80 ℃.
7. The method according to claim 1, wherein the Pd/TiN-ethanol dispersion liquid has a concentration of 5 to 8g/L and the binder has a concentration of 0.005 to 0.02g/L in S06.
8. Use of a Pd/TiN electrocatalytic electrode prepared according to any one of claims 1 to 6 for removing chlorine atoms from chlorine-containing wastewater.
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